Mineralization of renal tissue was investigated using Von Kossa's method and capillary gap technology. Combining these techniques allowed the simultaneous processing of 100 slides, reduced the volume of 5% silver nitrate required, and produced consistent dark brown to black silver deposits in positive control sections. A 25-fold savings in silver nitrate was achieved. By markedly reducing individual slide handling, technician time also was greatly reduced. Two or three slide sets, each containing approximately 100 slides, can be conveniently stained daily.